Underground storage of liquids



March 31, 1959 C, T, BRANDT A 2,879,646

UNDERGROUND STORAGE OF LIQUIDS Filed Feb. 15. 1954 PERvIOUs FORMATION I l' l l I l l IMPERVIOUS LAYER INVENTOR.

C.T. BRANDT ATTORNEYS United States Patent O UNDERGROUND STORAGE F LIQUIDS Carl T. Brandt, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application February 15, 1954, Serial No. 410,274

4 Claims. (Cl. 61.5)

This invention relates to a method and apparatus for underground storage of liquids having a specilic gravity less than that of a sealing uid, In one of its aspects, this invention relates to a method and apparatus for storing liquids having a specific gravity less than water in a subterranean pervious formation located between two substantially impervious strata. In still another aspect, this invention relates to a method of storing liquids or condensable gases having a specific gravity less than l in the pore space of a pervious rock formation lying between impervious strata.

In recent years, a great deal of attention has been given to underground storage of liquids or condensable gases. The underground storage containers are generally formed by mining operations in an impervious formation, dissolving soluble material such as rock salt by means of a solvent such as water, or these storage containers consist of preformed vessels which are buried underground. The type of storage container will be dependent upon the subsurface formation available.

As has been said, this invention relates to a subsurface storage container formed in a pervious formation lying between two impervious layers or strata. Storage containers of the prior art formed in sch formations are subject to one or more of the following disadvantages: they require complete excavation of the storage area: they depend upon ground water pressure to provide the impervious vertical and horizontal Water seal and recovery pressure; and/0r they require special pumping equipment for the stored material.

An object of this invention is to provide an improved underground storage chamber in a pervious subsurface formation lying between two impervious subsurface layers. Another object of this invention is to provide an improved underground storage chamber for liquids having a specific gravity less than that of a sealing fluid and wherein a fluid nonmiscible with the stored liquid is used as a barrier means and as a means for controlling the storage pressure.

The storage vessel of my invention comprises a defined volume of a pervious subsurface formation lying between two impervious strata. The volume of the pervious formation is encircled by a narrow tunnel connected to the surface by means of a shaft. The tunnel extends the full depth of the pervious stratum. The external wal1 of the tunnel is covered to retard fluid ow outwardly. An annular barrier or membrane impervious to the stored liquid at the low pressures encountered is placed within the tunnel a spaced distance from the outer wall so as to provide an annular space between this membrane and the outer wall. The said membrane projects downward from the upper impervious layer to a predetermined distance above the lower impervious layer thereby providing for communication between the said annular space and the storage space within the annular membrane. A cased well connects the storage space with the surface. Except for the tunnel, the storage space is not excavated,

the stored material being contained the pore space of the pervious formations.

The sealing fluid will be immiscible with the stored material and will be of a greater density than the material being stored. Since the sealing fluid may be lost to the surrounding earth, the usual sealing fluid will be water or brine. I will describe my invention in terms of water as the sealing iluid and liquid petroleum gas (LPG) as the stored product.

The stored material is contained by the annular membrane, the upper impervious layer and a water layer above the lower impervious layer. The water level will be above the lower edge of the projecting annular membrane. Water is contained in the shaft connecting the tunnel with the surface, the annular space between the membrane and the outside tunnel wall, and in the lower level of the pervious formation and thereby forming the lower boundary of the stored material. The water serves to balance the vapor pressure of the stored material, to reduce the pressure differential across the tunnel membrane and to displace product.

I will further explain and describe my invention by referring to the attached schematic drawing, which is a vertical, sectional view of an underground storage system constructed in accordance with the invention.

Referring to the drawing, a shaft 1 is sunk from the surface to the top of the lower impervious layer 2. A tunnel or drift 3 is then excavated circumscribing the space desired for storage. The top of the said tunnel will be the bottom of an upper impervious layer 4 and the bottom of the tunnel will be the top of the said lower impervious layer. The exterior wall of the tunnel will be coated by a substantially impervious material 5 forming an outer membrane. This outer impervious membrane can be grouted, cemented, rolled or otherwise applied and can be of any suitable material such as cement, plastic, metal, etc. The tunnel wall will support this membrane and a high pressure here will do no serious damage. This external membrane is usually sealed at both its top and bottom to the limpervious layers to prevent pressure leaks.

A second impervious membrane 6 is placed a predetermined distance within the external membrane and is spaced therefrom by spacers 7. This second membrane is sealed to and receives its main support from the roof or upper impervious layer 4 and projects therefrom downward to a position above the floor or lower impervious layer 2. This second membrane can be supported by means of block assembly 23 anchored to the impervious layer 4. This inner membrane can be supported from the floor so long as openings are provided for free fluid llow. This inner membrane can be of the same or different material than is the outer membrane. As will be seen later, the pressure difference across this inner membrane is small and consequently there is little danger of rupture. This inner membrane can be placed against the inner wall of the tunnel but if the tunnel is wide as it generally will be providing working room for mount- -ing the membranes, the effective storage space would be reduced by this amount. In order to obtain the maximum storage space, and to obtain lateral support for the membrane, the inner membrane is closely spaced to the outer membrane and providing for only a narrow column of water in the annular space between the two membranes. A cased well 8 extends from the high point within the storage space 9 to the surface. This well is generally cemented in place. The shaft 1 communicates with a water level vessel or standpipe 10 located above the earths surface. A device 11 is provided for maintaining the water level in the water level vessel.

In the operation of my invention, the shaft 1, the space between the two membranes, and the storage space will that of water.

geraete be filled 'with water. The material to be stored which I will illustrate by LPG (liquefied petroleum gas) is admitted under pressure via conduit 12, valve 13 and cased well 8 to the storage space 9. Valve 14 in conduit 15 will be closed. The LPG will force the water downward under membrane 6 and up shaft '1 into level device 10 to water reservoir 16 via conduit 17. The water level in the'storage space can be displaced to a level above the bottom of membrane 6. The pressure across the membrane 6 is small and will be dependent upon the difference in the specic gravity of the stored LPG and Since membrane 5 is supported by the surrounding soil, it will be able to withstand the pressure of the water against it. It is pointed out that small leakage through membrane 5 is not serious since such leakage can 'be easily replaced.

To remove LPG'from storage, valve 13 is closed and valve 14 is opened. Pump 18 is started and water from reservoir 16 is pumped to water'level vessel 10 via conduits 19 and 20. The hydrostatic head of water exceeds the hydrostatic head of LPG and forces the LPG up through well 8 and conduit 1S to further processing equipment (not shown). Make-up water is supplied to the reservoir via conduit 21. Valve 22 is provided in the well conduit 8 so that material can be sent directly to processing bypassing the storage area.

The liquid level control apparatus 11 can be automatically operated so as to maintain the desired level in water level vessel 10. I have shown the shape of the impervious membranes as being cylindrical. obvious to those skilled in the art that the shape of the storage space can be varied as desired without departing from the scope of this invention. Other modifications which can be made without departing from the scope of my invention will be seen by those skilled in the art.

I claim:

1. In an underground storage chamber formed in a porous formation lying between upper and lower impervious formations, the improvement comprising a tunneled space lying between the said impervious formation and circumscribing the storage volume in the porous formation, two spaced annular barriers in said tunneled space circumscribing the storage volume in the pervious formation, the outer barrier being adjacent the outer wall of said tunnel and sealed at both its top and bottom formation, and means for changing the level of the underlying body of liquid thereby changing the storage volumes.

2. An underground storage apparatus comprising vin combination two spaced impervious membranes in a tunnel'surrounding a subsurface porous formation lying between upper and lower impervious formations, the outer membrane being sealed at its top and bottom to the imperviouslayers and being supported by the surrounding soil, the inner membrane being sealed to the upper impervious layer rand projecting downward to a spaced position above the lower impervious layer; a conduit connecting the interspace between the two layers with a water level chamber on the earths surface, the said conduit, Water level chamber and interspace between the two membranes beinglled with water which communicates with it will be a body of water underlying the porous formation; means for 'maintaining the water level in the water level chamber; and a conduit communicating from a high point of the porous formation to the surface.

3. An underground storage apparatus adapted for storage of fluids, having a specific gravity less than l, the said apparatus comprising in combination an annular tunnel excavated in a porous formation, the said porous formation lying between an upper and a lower subsurface impervious formations, the roof of said tunnel being the upper impervious formation and the floor being the lower impervious formation; an impervious membrane covering the outside wall of the said tunnel the said membrane being `sealed atits top and bottom to the said impervious formations; a second annular impervious membrane supported in spaced relationship within and from the rst said impervious membrane, the second said membrane being sealed to the upper impervious formation andprojecting downward to a spaced distance above the tunnel iloor; a Water level vessel disposed upon the earths surface; means for adding and withdrawing water from vthe said water level vessel and maintaining a constant level therein; a conduit communicating between the said'water level vessel and the annular interspace formed between the said two impervious membranes; water in the said water level vessel, the said conduit and the interspace between the two membranes, the said water communicating with a body of water underlying the porous formation enclosed by the said tunnel; and a conduit communicating between the said enclosed porous formation andthe earths surface.

4. A method of forming an underground storage volume in a pervious formation lying between two impervious layers the said method vcomprising drilling a shaft from the surface through the upper impervious layer to the lower impervious layer; excavating an annular tunnel starting fromlthe said shaft and circumscribing the desired storage volume in the pervious formation, the said tunnel extending vertically from the upper impervious layer to the lower impervious layer; applying an impervious membrane on the 'outer wall of the said tunnel, sealing the said membrane to the upper and lower impervious layers; sealing a second annular impervious membrane within the tunnel from the upper impervious Vlayer a predetermined distance from the outer membrane, the second said membrane projecting from the upper impervious layer to a predetermined distance above the lower impervious layer providing for an annular space between the two membranes, the annular space cornmunicating freely with the said shaft; drilling a second shaft from the earths surface through the upper impervious layer to a high point in the pervious formation; and cementing'a casing in the second said shaft the last said casing extending from the surface to a position within the upper impervious layer.

References Cited in the le of this patent UNITED STATES PATENTS 1,006,912 ACook Oct. 24, 1911 1,628,635 Laird May 10, 1927 1,921,358 Hill et al. Aug. 8, 1933 2,579,005 Lambert Dec. 18, 1951 2,659,209 Phelps Nov. 17, 1953 2,661,062 Edholm Dec. l, 1953 OTHER REFERENCES Oil and YGas JournalfofMar. 9, 1953, page 109. Oil and Gas Journal of Aug. 17, 1953, page 84. 

